\begin{table}[H]
\centering\centering
\caption{\label{tab: estimation - demand}Demand substitution elasticities.}
\centering
\begin{tabular}[t]{lcccccc}
\toprule
\multicolumn{1}{c}{ } & \multicolumn{6}{c}{Dep. var.: log (expenditure share)} \\
\multicolumn{1}{c}{ } & \multicolumn{2}{c}{Lower level} & \multicolumn{2}{c}{Middle level} & \multicolumn{2}{c}{Upper level} \\
\multicolumn{1}{c}{ } & \multicolumn{2}{c}{(across counties)} & \multicolumn{2}{c}{(across nations)} & \multicolumn{2}{c}{(across commodities)} \\
\cmidrule(l{3pt}r{3pt}){2-3} \cmidrule(l{3pt}r{3pt}){4-5} \cmidrule(l{3pt}r{3pt}){6-7}
  & OLS & IV & OLS  & IV  & OLS   & IV  \\
\midrule
log (price) & 1.266*** & -8.641*** & -1.478*** & -4.992*** & -1.030*** & -4.107**\\
 & (0.020) & (0.691) & (0.079) & (0.772) & (0.163) & (1.173)\\
\midrule
KP-Wald First stage F-statistic &  & 257 &  & 32 &  & 9\\
Observations & 409558 & 409558 & 38272 & 38272 & 4059 & 4059\\
\bottomrule
\multicolumn{7}{l}{\rule{0pt}{1em}Notes:}\\
\end{tabular}
\end{table}
